Without oil or, depending on the food, with a tiny bit of oil. Brush it on or mix it in a bowl.

Yes, I was supplied with an adapter and yes, you can airfry without additional oil. A little oil is recommended for some foods. We are very satisfied :-).

Theoretically yes, but we always toss vegetables or chips in oil beforehand and then put them in the deep fryer.
Greetings
Peter